The present invention relates to an error correcting technique employed for transmitting highly reliable information even under poor channel environment in a transmission system of a high definition television (hereinafter simply referred to as "HDTV"), and more particularly to a sync detecting apparatus and method thereof for effectively detecting a sync signal from a signal received in a receiver of a HDTV to perform interleave/deinterleave of the error correcting technique.
In connection with receivers of HDTVs, U.S. Pat. No. 5,200,811 discloses a technique wherein a received signal is separated into narrow and intermediate frequency (IF) bands, and the signal separated into the narrow and IF bands is locked to a predetermined stable frequency to demodulate the separated if by quadrature phase, and respective signals demodulated by quadrature phase are low-pass filtered to be converted into digital data. Then, data converted from the digital data is delayed for a predetermined time, and mixed with a signal processed in a high band, so that the obtained result is separated into a luma signal and a color difference signal to be converted into an analog signal. As a result, the audio/video receiving apparatus becomes compatible with existing color televisions. In brief, the technique employed in the above patent is a decoding used for reception by means of band separation and sub-sampling methods.
On the other hand, for executing the deinterleave in a receiver of an HDTV, a sync signal is detected from a received signal, and rotation compensation is performed by recognizing a rotated amount of the received signal.
The above-stated two operations are the function of a sync detector.
Meanwhile, in a frame format suggested in the channel compatible digicipher HDTV system (CCDC), an initial three bytes are used for the synchronization of the deinterleave.
That is, a reference signal of a symbol unit capable of being used for the synchronization numbers six.
In the present invention, five signals are utilized as the reference signals, and the remaining one signal is used as an additional signal to be employed in setting up the system.
When an encoding is executed in a trellis encoder, space for involving six signals is not encoded but filled with preset five reference signals and one additional signal.
The receiver compares the transmitted signal with the preset reference signals to detect the sync signal required for the deinterleave.